1. Field of the Invention
The present invention is relates to a synthesis method of a new material Si.sub.X C.sub.Y N.sub.Z in crystalline form on a crystalline substrates having appropriate lattice parameters and orientation for forming said material thereon.
2. Description of the Prior Art
Cohen M. L. [Phys. Rev. B, 32, 7988(1985)] has predicted high bulk modulus for covalently bonded carbon-nitrogen solid material. Particularly, .beta.-C.sub.3 N.sub.4, which is a carbon-nitride material with a crystal structure identical to that of .beta.-Si.sub.3 N.sub.4, was predicted to have exceptionally high bulk modulus and was thus predicated to be as hard as or even harder than diamond (Liu A. Y. and Cohen M. L., Science, 245, 941(1989)). Although this prediction greatly stimulated research for experimental realization of this material, to our knowledge, covalently bonded crystalline carbon-nitride solids with crystal sizes large enough to enable measurement of various physical and chemical properties have heretofore not been synthesized in any of the crystal phases, let alone the .beta. phase. Some researchers have only succeeded in synthesizing very tiny crystals (crystal size typically between 0.01 to 0.5.mu.)of carbon-nitride, embedded in the amorphous CN matrix, wherein volume of the crystalline phase accounts for less than 5% of the total volume of deposited material (Haller E. E., Cohen M. L. and Hansen W. L., U.S. Pat. No. 5,110,679(1992)).
Silicon nitride, in both of its crystalline phases .alpha. and .beta. in itself is of considerable interest for its applications as high performance engineering material because of its strength, high decomposition temperature and excellent resistance to corrosion and wear. Moreover, owing to its low mass density, it offers a light weight material for fabrication of components with excellent strength-to-weight ratio. For the same reasons, carbon-nitride, in any of its crystalline phases .alpha. or .beta., is even more desirable for such application.
However, since crystalline carbon-nitride has so far eluded the researchers while amorphous CN is readily realized (Okada T., Yamada S. and Wada T., Japanese Patent No.JP8-158039(1996), Okada T., Yamada S. and Wada T., Japanese Patent No.JP8-158040(1996), Fujikawa T. and Fujita N., Japanese Patent No., JP 3-240959(1991), Shimada T., Watanabe S. and Nakashi A., Japanese Patent No., JP 3-197364(1991), Suzuki S., Japanese Patent No. 61-174377(1986)), the present inventors believed that incorporation of a small quantity of silicon during the growth of carbon-nitride would bring about improvement in the crystalline quality of the resulting material, since Si is known to readily form a well crystalline material with composition Si.sub.3 N.sub.4, in either a or : phase. It was further believed that a substantial fraction of carbon would get incorporated in the crystalline form, thereby resulting in formation of new material with either of the known SiN crystal structures but with Si and C atoms interchangeably occupying the fourfold Si sites in the corresponding SiN structure. Such material is also expected to possess all the desirable properties of SiN or CN, such as high bulk modulus, high hardness, low mass density, high strength, wide optical band gap, high electrical resistance, high decomposition temperature, chemical innertness, resistance to wear and corrosion, high thermal conductivity etc.